The correct answer is - Spain.
The Spanish, were the first ones to get to the territories of the Americas, soon to be followed by the Portuguese. After their initial disagreements, a treaty was concluded, the treaty of Torsedillas, with which the Spanish were granted all the territories on the western part of the Americas.
The Spanish used this as quick as possible, and the rushed to conquer the new lands and people, and get hold on the riches. They managed to get hold on Central America, the western part of South America, and the western part of what is nowadays the United States, and managed in that time, to be the largest empire in the world.